Experimental infection of squirrel and marmoset monkeys with attenuated Herpesvirus saimiri.

Herpesvirus saimiri (HVS) was propagated in vero cells for 3 passages at 39 degrees and cloned 3 times at 34 degrees. This virus was inoculated into cotton-topped marmoset and squirrel monkeys; all inoculated monkeys became infected as HVS was reisolated after their circulating lymphocytes were cultured with vero cells and measurable levels of antiviral antibodies developed that were measured by immunofluorescence and/or neutralization tests. None of the inoculated monkeys developed any signs of overt disease and all inoculated monkeys have survived 9 to 14 months postinoculation. The attenuated virus appears to be genetically stable as virus isolated from an infected marmoset was passed 3 times in vitro and then inoculated into other marmosets, which became infected and remained clinically well. Marmosets latently infected with attenuated HVS were not protected when challenged with a large dose (770 plaque-forming units) of oncogenic HVS, although these marmosets survived about 3 times longer than did inoculated control marmosets.